This invention relates to vehicle batteries and, in particular, to a method and apparatus for controlled heating of vehicle batteries.
It is well known that the operation of batteries in vehicles is affected by ambient temperature. As ambient temperature drops, the internal voltage of these conventional batteries decreases and the internal resistance rises. As a result, conventional batteries can become incapable of operating in accordance with their intended functions (e.g., starting the vehicle engine) if the temperature is too low.
In order to overcome the affects of low ambient temperatures, a variety of devices have been developed to warm batteries responsive to low temperatures. Available battery power is dependent on the battery""s charge condition in addition to temperature, however, and conventional devices fail to take account of the charge condition of the battery. As a result, conventional devices are subject to inefficiencies because warming of the battery is handled in the same manner regardless of the battery""s charge condition.
There is thus a need for a circuit and a method for controlling a battery that will minimize or eliminate one or more of the above-mentioned deficiencies.
The present invention provides a circuit and a method for controlling a battery.
A circuit in accordance with the present invention includes a switching device disposed between first and second poles of the battery and responsive to a control signal. When closed, the switching device shorts the battery thereby generating heat due to internal resistance of the battery. The circuit also includes a controller that generates the control signal in accordance with a predetermined algorithm responsive to a temperature of the battery and a voltage drop across the first and second poles of the battery.
A method for controlling a battery in accordance with the present invention includes the step of providing a switching device between first and second poles of the battery. The method further includes the step of controlling the switching device responsive to a temperature and a voltage drop across the first and second poles of the battery. The step of controlling the switching device may include several substeps including the substeps of measuring the temperature and the voltage drop across the poles of the battery and comparing the measured temperature and voltage drop to a predetermined temperature and voltage drop, respectively. The controlling step may further include the substep of closing the switching device whenever the measured temperature and voltage drop meet predetermined characteristics relative to the predetermined temperature and voltage drop. For example, the switching device may be closed when the measured temperature is less than the predetermined temperature and the measured voltage drop is greater than the predetermined voltage drop.
A battery control circuit and method in accordance with the present invention represent a significant improvement as compared to conventional battery control devices and methods. In particular, the inventive circuit and method warm the battery responsive to both a temperature and the charge condition of the battery in a highly controlled manner. As a result, unnecessary warming of the battery is minimized and operating efficiencies improved.
These and other advantages of this invention will become apparent to one skilled in the art from the following detailed description and the accompanying drawings illustrating features of this invention by way of example.